Glazing

ABSTRACT

A curved laminated automotive glazing panel ( 10 ) having a radius of curvature at at least one portion that is less than 500 mm has a glazing panel which is provided with a solar control coating layer ( 25 ) positioned at its convex internal surface ( 11 ) and in which the coating stack comprises at least two space sputtered silver containing layers initially deposited on a substantially flat sheet of glazing material which is subsequently bent to form a part of the glazing panel ( 10 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage of International ApplicationNo. PCT/EP00/08205 filed 21 Aug. 2000, and European Application No.99202757.3 filed 26 August 1999. The entirety of each of thoseapplications is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to laminated automotive glazing panels providedwith solar control coating layers. Whilst the invention will beparticularly described with reference to vehicle windscreens it shouldbe understood that it may have other applications.

The use of coating layers is well know to modify the optical propertiesof glazings. In particular, coating layers may be used to reduce theproportion of incident solar energy which is transmitted through theglazing whilst allowing passage of sufficient visible light to ensuregood visibility. This can reduce overheating of the interior of thevehicle in summer and is commonly achieved by reflection of incidentsolar radiation in the infra-red portion of the spectrum. Coating layersmay also provide an electrically heatable element for a glazing.EP378917A (Nippon Sheet Glass Co.) discloses such coating layers.

The term solar control coating layer as used herein refers to a coatinglayer which increases the selectivity of the glazing panel i.e. theratio of the proportion of incident visible radiation transmittedthrough the glazing to the proportion of incident solar energytransmitted through the glazing.

The term luminous transmittance as used herein means the luminous fluxtransmitted through a substrate as a percentage of the incident luminousflux measured using CIE Illuminant A at 2° observer.

There are a number of different families of solar control coatinglayers, each of which have differing properties and characteristics.These include:

a) pyrolytic coatings obtained by contacting a liquid or vapourcomposition with the hot surface of a glass sheet. Such coatings includetin oxide coatings doped with fluorine and indium tin oxide (ITO)coatings. Pyrolytic coatings have the general characteristic of beinghard coatings (i.e. they are relatively resistant to abrasion) and ofbeing relatively easy to handle during manufacturing processes withoutdamage to the coating layer. Many pyrolytic coatings are inherently heatresistant to a sufficient extent to enable glass sheets to which theyare applied to be bent and/or thermally tempered without significantdeterioration of their solar control properties. A significantindustrial advantage results from the ability to apply pyrolyticcoatings to a continuous ribbon of flat glass for example as part of aprocess of making float glass. European patent application EP 353 141 A(Saint Gobain Vitrage) describes a heatable pyrolytic indium tin oxidecoating on face 3 of a laminated windscreen. Such glazings have neverfound commercial success in the automotive field due particularly to theinherent optical and energetic limitations of this type of coating.

b) Sputtered single silver layer coatings obtained by sputtering asilver containing layer on to a supporting substrate. Such coatingsusually comprise a coating stack having the general form: supportingsubstrate antireflective layer optional barrier layer/silver containinglayer/optional barrier antireflective layer. In such a structure thesilver containing layer serves to reflect radiation in the infra redportion of the spectrum, the antireflective layers serve to reducereflection of light in the visible portion of the spectrum that wouldotherwise be caused by the silver containing layer and the optionalbarrier layers serve to protect to silver continuing layer either duringdeposition of the coating and/or subsequent processing. Whilst theoptical performance of single silver layer sputtered coatings isreasonably good such sputtered coatings are general “soft” coatings i.e.they are not particularly resistant to abrasions and scratches andrequire significant care in handling to avoid damage. In addition,significant care in both the design and handling of such layers isrequired to enable them to be sufficiently heat resistant to allowtempering and/or bending of a substrate to which they are applied.

c) Sputtered double silver layers obtained by sputtering two, spacedsilver layers onto a supporting substrate. Such coatings usuallycomprise a coating stack having the general form: supportingsubstrate/antireflective layer/optional barrier layer/silver containinglayers optional barrier layer/antireflective layer/optional barrierlayer/silver containing layer/optional barrier antireflective layer. Insuch a structure the sliver containing layers serve to reflect radiationin the infra red portion of the spectrum, the antireflective layersserve to reduce reflection of light in the visible portion of thespectrum that would otherwise be caused by the silver containing layerand the optional barrier layers serve to protect to silver containinglayers either during deposition of the coating and/or subsequentprocessing. The infra red reflective silver containing layers arecommonly layers of silver or a silver alloy have a thickness in theorder of 80 to 120 Å. The optical performance of double silver Layersputtered coatings can be extremely good, especially in terms of theirselectivity but perhaps even more so than with single silver sputteredcoatings these coatings are extremely fragile both in terms ofresistance to abrasions and scratches (for example during handling) andin their ability to withstand heating for example to enable them to besufficiently heat resent to allow tempering and/or bending of asubstrate to which they are applied.

One example of the use of sputtered coating layers In automotiveapplications is U.S. Pat. No. 4,668,270 (Ford Motor Company) whichdescribes a car windscreen having an electrical heatable coating layerused for defrosting, de-icing and/or de-misting. The heatable waling,which is laminated between the two glass sheets of the windscreen, issupplied with electrical power via first and second bus bars whichextend respectively along the top and bottom edges of the windscreen,each bus bar being silk screen printed on the glass in a silver ceramicmaterial. The heatable coating is a multilayer coating consisting ofzinc oxide and silver formed by magnetron sputtering.

The physical nature of double silver layer coatings layers is entirelydifferent to tat of, for example, pyrolytic coating layers and,consequently, entirely to different techniques must be employed fortheir design, processing and use.

It has generally been believed in the art that the precautions of thetechniques described below must be adhered to to enable the successfuluse of sputtered double silver layers In laminated automotive glazings:

1) that the sputtered double silver layers should be deposited on acarrier film of, for example pet (poly ethylene tetrachloride), which isassembled between the to glass sheets of a laminated glazing once theindividual sheets have been bent to their desired final shape. Onedisadvantage of such carrier films is the difficulty of ensuring thatthe film correctly follows then precise contour of the bent glazingpanel. Consequently, this procedure is limited to use with glazingpanels of a relatively simple curvature. In addition, it is generallynot desirable to electrical heat the solar control coating in such anarrangement due to deterioration of the coating and/or of the carrierfilm and it is also inconvenient to provide bus bars in this arrangementto relay electrical power to the coating. Consequently, this techniqueis generally unsuitable for use with heatable windscreens.

2) that, alternatively, the sputtered double silver layers should beapplied to the concave face of a pre-bent sheet of glass prior to itsassembly to form a laminated glazing panel. In this way, the coatinglayer is not subjected to the heat treatment necessary to form thedesired curvature of the glass sheet disadvantages of his techniqueinclude the technical difficulty of sputter depositing coating layersonto a curved sheet of glass so as to ensure that the entire glasssurface is evenly coated (due, amongst other things, to the variation inthe distance between the different part of the glazing surface and hetargets used for the sputtering process-small variations in thickness ofthe coating layers can cause undesirable colour variations across theglazing panel) and the complexity and limitations (including dimensionallimitations-complex windscreens having deep curvatures will not alwaysfit in to such coating machines simply because of their dimensions) ofcoaters which can sputter deposit layers onto a curved substrate.Consequently, this technique is also limited to use with relativelysimple curvatures of glazing panels.

3) alternatively, sputter depositing a double silver coating layer ontoa relatively flat sheet of glass and subsequently bending the glasssheet carrying the coating stack to its desired shape prior to assemblyas a laminated glazing panel Due to the fragility of this type ofcoating, the glass sheet carrying the coating stack should be bent suchthat the coating stack is at the concave face of the curved sheet ofglass. This is so that the layers of the coating stack have a tendencyto be compressed during the bending process so as to ensure theintegrity and continuity of the to layers of the coating stack, this isparticularly so for complex curvatures of glaring

SUMMARY OF THE INVENTION

Thus, in order to successfully use a sputtered double silver layercoating on a complex curved glazing panel it is necessary either todeposit the coating onto a pre-curved glazing panel or to use a heattreatable sputtered double silver layer coating deposited on asubstantially flat sheet of glass which is subsequently bent so that thecoating is at its concave surface.

According to one aspect, the present invention provides a method ofmaking a laminated automotive glazing panel having a radius of curvatureat at least one portion that is less than 500 mm comprising the stepsof:

-   -   a) depositing a solar control coating layer comprising a coating        stack having at least two spaced sputtered silver containing        livers on a substantially flat sheet of glazing material:    -   b) bending said substantially flat sheet of glazing material        carrying said solar control coating layer such that the solar        control coating layer is positioned at a convex surface of the        bent sheet of glazing material, and    -   c) laminating said bent sheet of glazing material carrying the        solar control coating layer at a convex surface with another        sheet of glazing material to form a glazing panel in which the        solar control coating layer is positioned at the interior of the        laminated glazing panel.

The invention results from the unexpected realisation that despiteprejudice in the art, a complex shape of glazing panel incorporating asputtered double silver layer coating may be produced on an industrialscale by depositing the coating on a substantially flat sheet of glassand subsequently bending the glass sheet carrying the coating such thatthe coating is at the convex surface of the glazing panel This ispossible despite the fact that subjecting the sputtered double silvercoating layer to the tension an extension inherent in bending it into aconvex shape would be expected to destroy the integrity and continuityof the coating layer and perhaps even to rest in significant disparitiesin the thickness of the coating layer over the area of the glazingpanel. The realisation that this is possible with relatively complexcurvatures is even more surprising firsty because complex curvaturesrequire significant degrees of bending and would thus be expected tocause unacceptable tension and extension of the coating layer andsecondly because complex curvatures require the heating of the glasssubstrate to a softening level at higher temperature and/or for a longerduration that simple curvatures and would thus be expected to putadditional unacceptable stuns on the relatively fragile sputtered doublesilver coating layer.

One factor which may be used to define the complexity of curare of anautomotive glazing is the radius of curvature. The smaller the radius ofcurvature, the more difficult it becomes to accurately and repeatablebend the glazing panel.

The present invention may be used in association with glazing panelshaving a radius of curvature at at least one portion that is less than450 mm, less Can 400 mm, less than 350 mm, less than 300 mm, less than250 mm, less than 200 mm, less than 150 mm or even less.

According to another aspect, the present invention provides a method ofmaking a laminated automotive glazing panel having a cross curvature ofgreater than or equal to 15 mm comprising the steps of:

-   -   a) depositing a solar control coating layer comprising a coating        stack having at least two spaced sputtered silver containing        layers on a substantially flat sheet of glazing material;    -   b) bending said substantially flat sheet of glazing material        carrying said solar control coating layer such that the solar        control coating layer is positioned at a convex surface of the        bent sheet of glazing material;    -   c) laminating said bent sheet of glazing material carrying the        solar control coating layer at a convex surface with another        sheet of glazing material to form a glazing panel in which the        solar control coating layer is positioned at the interior of the        glazing panel.

Another factor that may be used to define the complexity of curvature ofan automotive glazing panel is it cross curvature. This is a measurementof the depth of curvature across the height of the glazing at thecentral portion of the glazing panel.

The present invention may be used in association with gang panels havinga cross curvature Eat is at least 15 mm, at least 20 mm, at least 25 mm,at least 30 mm, at least 35 mm or greater.

The curvature of the glazing panel becomes even more complex when, forexample, a significant minimum radius is combined with a significantcross curvature.

A further factor which may add to the complexity of curvature of anautomotive glazing panel is the depth of bending. This is a measure ofthe greatest distance between the front face of the glazing panel andthe end of the rearwardly projecting side wings of the glazing panel.The present invention may be used in association with a depth of bendingof at least 150 mm, at least 170 mm, at least 190 mm, at least 200 mm,at least 220 mm, at least 240 mm, at least 250 mm or more.

The complexity of curvature is further increase if a significant depthof bending is combined with a significant minimum radius of curvatureand/or a significant cross curvature.

The present invention may advantageously be used to provide a de-mistingand/or de-icing function to the glazing by using a coating layer whichis electrically heatable and pervading a pair of spaced bus bats torelay elect current to the coating layer. The exposed concave surface ofa laminated windscreen is generally at the Interior of the vehicle.Positioning the coating layer on the convex surface sandwiched betweenthe two glazing panels of the laminated structure may provide a numberof advantages with respect to positioning a heatable sputtered doublesilver coating layer at the concave surface sandwiched between the twoglazing panels of the laminated structure. These may include:

-   -   a) an improved de-misting function as the heatable coating layer        is directly adjacent to the sheet of the glazing panel at the        interior of the vehicle:    -   b) a reduced risk of damaging the integrity of the coating layer        in the case of a breakage or crack of the outer sheet of the        gazing panel, for example due to the impact of gravel. Any        discontinuity in the coating layer may cause a break in its        electrical conductivity and a consequent overheating of        immediately surrounding areas of the coating layer when elected        current passes. Such overheating may cause deterioration of the        coating layer and/or deterioration of the laminating film        between the two sheets of the glazing panel In addition, the        position of the to coating product it at least to some degree        from the risk of corrosion by the ingress of moisture in the        case of a breakage or crack in the outer sheet of the glazing        panel.

An additional advantage of the defined positioning of the coating layerin association with the provision of bus bars is the ability the hidethe bus bars from view from the exterior of the glazing panel byproviding a substantially opaque masking layer, for example a blackenamel layer, around a portion of the into concave sur of the glazingpanel.

The complexity of curvature is Ceased in respect of glazing panelshaving a significant width, for example, glazing panels at are between1.2 m and 1.4 m wide, or between 1.4 m and 1.6 m wide or between 1.6 mand 1.8 m wide.

The invention may be partials suitable for use in relation to vehiclewindscreens.

The glazing panel may have a luminous transmittance of greater than 70%or greater than 75%. This may enable its use as a windscreen

The glazing panel may have a neutral colour in reflection from itsexterior surface, a slightly blue colour or a slightly green colour.This may render it particularly suitable for use in automotiveapplications. In particular, the colour of the glazing panel inreflection from the exterior may be such that its colour coordinatesmeasured on the CIElab scale at normal incidence are:

-   -   L*=40±3 a*=−6±3 b*=−8±4 (this is intended to give a blue tint in        reflection, particularly for a windscreen installed at an        angel); or    -   L*=39±3 a*=−6±3 b*=−2±2 (this is intended to give a green tint        in reflection, particularly for a windscreen installed at an        angle); or    -   L*=36±3 a*=−5±2 b*=−4±2 (this is intended to give a        neutral/green tint in reflection, particularly for a windscreen        installed at an angle);

The variation is colour In reflection over the surface of the glazingpanel may be such that when measured at different points over a singleglazing, the values of either a* and/or b* measured on the CIElab scaleat normal incidence do not vary by more than ±1.5, and preferably by notmore than ±1. The variation in colour in reflection is due at least to asignificant extent upon variations in the thickness of the film stacksof the coating layer and/or variations in the heating regime during heattreatment over different parts of the glazing. It is perhapsparticularly unexpected that such minimal colour variation can beachieved by means of the present invention as it would be expected theextension of the coating layer would stretch the coating layer, at leastin some places and/or des*W the integrity of the coating layer and/ortender It unstable during heat treatment

Preferably, the variation in colour In reflection between one glazingand another is such that the values of either a* and/or b* measured onthe CIElab scale at normal incidence do not vary between one glazing andanother in a series of glazings by more than ±2, and preferably by notmore than±1.5.

Arranging the resistance of the heatable coating layer to be betweenabout 1.5 and 4 ohms per square may provide particularly suitableheating characteristics for automotive use. Similarly, arranging for theresistance between the bus bars to be between 75 ohm and 8 ohm may aprovide particular suitable heating characteristic for automotive use.

According to further aspects, the present invention also provides acurved laminated glazing panel, as defined in claims 15 and 17, and forthe use of a sputtered double silver coating layer deposited on asubstantially flat sheet of glazing material and subsequently bent intoa convex configuration to provide a glazing panel as defined in claim29.

The glazing material onto which the solar control coating layer isdeposited may be a sheet of glass. It is preferably a soda-lime glass,more preferably float glass. It may comprise the following constituent(expressed in percentage by weight):

SiO₂ 60 to 75% Na₂O 10 to 20% CaO  0 to 16% K₂O  0 to 10% MgO  0 to 10%Al₂O₃ 0 to 5% BaO 0 to 2% BaO + CaO + MgO 10 to 20% K₂O + Na₂O 10 to 20%

An embodiment of the present invention will now be described, by way ofexample only, with reference to: values of either a* and/or b* measuredon the CIElab scale at normal incidence do not vary by more than ±1.5,and preferably by not more than ±1. The variation in colour inreflection is due at least to a significant extent upon variations inthe thickness of the film stacks of the coating layer and/or variationsin the heating regime during heat treatment over different parts of theglazing. It is perhaps particularly unexpected that such minimal colourvariation can be achieved by means of the present invention as it wouldbe expected that extension of the coating layer would stretch thecoating layer, at least in some places and/or destroy the integrity ofthe coating layer and/or render it unstable during heat treatment.

Preferably, the variation in colour in reflection between one glazingand another is such that the values of either a* and/or b* measured onthe CIElab scale at normal incidence do not vary between one glazing andanother in a series of glazings by more than ±2, and preferably by notmore than ±1.5.

Arranging the resistance of the heatable coating layer to be betweenabout 1.5 and 4 ohms per square may provide particularly suitableheating characteristics for automotive use. Similarly, arranging for theresistance between the bus bars to be between 0.75 ohm and 8 ohm mayalso provide particularly suitable heating characteristics forautomotive use.

According to further aspects, the present invention also provides acurved laminated glazing panel having a radius of curvature at least oneportion that is less than 500 mm in which the glazing panel is providedwith a solar control coating layer positioned at its convex internalsurface and in which the coating stack comprises at least two spacedsputtered silver containing layers initially deposited on asubstantially flat sheet of glazing material which is subsequently bentto form a part of the glazing panel. A curved laminated automotiveglazing panel is also provided having a cross curvature of greater thanor equal to 15 mm in which the glazing panel is provided with a solarcontrol coating layer positioned at its convex internal surface and inwhich the coating stack comprises at least two spaced sputtered silvercontaining layers initially deposited on a substantially flat sheet ofglazing material which is subsequently bent to form a part of theglazing panel.

The use of a sputtered double silver coating layer which is initiallydeposited on a substantially flat sheet of glazing material andsubsequently bent into a convex configuration to provide a glazing panelis also provided. The curved laminated automotive glazing panel can havea radius of curvature at at least one portion that is less than 500 mmin which the glazing panel is provided with a solar control coatinglayer positioned at its convex internal surface and in which the coatingstack comprises at least two spaced sputtered silver containing layersinitially deposited on a substantially flat sheet of glazing materialwhich is subsequently bent to form a part of the glazing panel.According to this embodiment, the glazing panel can have a radius ofcurvature at at least one portion that is less than 400 mm, preferablyless than 350 mm and even more preferably less than 300 mm.Alternatively, the curved laminated automotive glazing panel can have across curvature of greater than or equal to 15 mm in which the lazingpanel is provided with a solar control coating layer positioned at itsconvex internal surface and in which the coating stack comprises atleast two spaced sputtered silver containing layer initially depositedon a substantially flat sheet of glazing material which is subsequentlybent to form a part of the glazing panel. The glazing panel as set forthabove can also have a cross curvature of greater than or equal to 20 mm,preferably greater than or equal to 25 mm and even more preferablygreater than or equal to 30 mm. Additionally, the glazing panel can alsohave a death of bending that is greater than or equal to 150 mm.Further, the coating layer can be adapted to be electrically heatable toprovide a de-misting and/or de-icing function to the glazing panel andin which the glazing panel is provided with a pair of spaced bus barsadapted to relay electrical power to heat the solar control coatinglayer. The glazing panel can also be provided with a substantiallyopaque band arranged at the internal, concave surface of the glazingpanel adapted to mask the bus bars from view from the exterior of thegazing 2 panel. Further, the glazing panel can have a width of greaterthan about 1.6 m. The glazing panel can be an automotive windscreen.Additionally, the glazing panel can have a luminous transmittance of atleast 75% (measured using Illuminant A, 2 degree observer). According toa further embodiment, the color of the glazing panel in reflection fromthe exterior is such that the color co-ordinates of the glazing panel inreflection from the exterior measured on the CIElab scale at normalincidence are within the range:

L* = 40 ± 3 a* = −6 ± 3 b* = −8 ± 4; or L* = 39 ± 3 a* = −6 ± 3 b* = −2± 2; or L* = 36 ± 3 a* = −5 ± 2 b* = −4 ± 2.According to an additional embodiment, the color variation in reflectionover the surface of the glazing panel is such that when measured atdifferent points over a single glazing, the values of either a* and/orb* measured on the CIElab scale at normal incidence do not vary by morethan ±1.5, and preferably by not more than ±1. Further, the electricalresistance of the heatable coating layer can be between 1.5 and 4 ohmsper square. The glazing panel can also be provided with a pair of spacedbus bars adapted to provide electrical power to heat the solar controlcoating layer and in which the resistance between the bus bars isbetween 0.75 and 8 ohms.

The glazing material onto which the solar control coating layer isdeposited may be a sheet of glass. It is preferably a soda-lime glass,more preferably float glass. It may comprise the following constituent(expressed in percentage by weight):

SiO₂ 60 to 75% Na₂O 10 to 20% CaO  0 to 16% K₂O  0 to 10% MgO  0 to 10%Al₂O₃ 0 to 5% BaO 0 to 2% BaO + CaO + MgO 10 to 20% K₂O + Na₂O 10 to 20%

BRIEF DESCRIPTION OF THE FIGURES

An embodiment of the present invention will now be described, by way ofexample only, with reference to:

FIG. 1 which is an exploded view showing the overall structure (but notthe curvature) of a windscreen;

FIG. 2 which is a plan view of a curved, laminated, automotivewindscreen;

FIG. 3 which is a section along line 3—3 of FIG. 2; and

FIG. 4 which is a section along line 4—4 of FIG. 2.

DETAILED DESCRIPTION

Windscreen 10 illustrated in FIG. 1 comprises an inner sheet of glass 11laminated to an outer sheet of glass 13 by means of a sheet of pvb 12.

The windscreen is substantially trapezial in shape having a top edge 21,a longer bottom edge 23 substantially parallel thereto and side edges22, 24 The windscreen has a spherical, curved configuration so that itis curved both along an axis parallel to the top edge 21 and along anaxis perpendicular to the top edge 21 (for ease of representation thecurvature of the windscreen is not shown in FIG. 1).

An electrically conducting solar control layer 25 comprising a sputtereddouble silver coating layer is positioned on the convex face of theinner glazing sheet 11 between the inner and outer sheets of glass11,13.

The coating layer 25 is produced by sputtering the following layerssequentially onto a substantially flat sheet of glass which issubsequently bent to form the inner glazing sheet 11:

Geometrical thickness Atomic ratios Glass substrate 2 mm Base dielectriccomprising: AlN  60 Å ZnAlOx 250 Å Al/Zn = 0.1 ZnAlOy underlying barrier 10 Å Al/Zn = 0.1 Ag 100 Å ZnAlOy overlying barrier  12 Å Al/Zn = 0.1Central dielectric 750 Å Al/Zn = 0.1 comprising ZnAlOx ZnAlOy underlyingbarrier  7 Å Al/Zn = 0.1 Ag 100 Å ZnAlOy overlying barrier  17 Å Al/Zn =0.1 Top dielectric comprising: ZnAlOx 185 Å Al/Zn = 0.1 AlN  85 Å

in which ZnAlOx is a mixed oxide containing Zn and Al deposited in thisexample by reactively sputtering a target which is an alloy or mixtureof Zn and Al in the presence of oxygen.

Alternatively, a mixed oxide layer may be formed by sputtering a targetwhich is a mixture of zinc oxide and aluminum oxide particularly in anargon gas or argon rich oxygen containing atmosphere.

The ZnAlOy barriers are similarly deposited by sputtering a target whichis an alloy or mixture of Zn and Al in an argon rich oxygen containingatmosphere to deposit a barrier that is not fully oxidised.

The oxidation state in each of the base, central and top ZnAlOxdielectric layers need not necessarily be the same. Similarly, theoxidation state in each of the ZnAlOy barriers need not be the same.Equally, the Al/Zn ratio need not be the same for all of the layers; forexample, the barrier layers may have a different AV/Zn ratio to theantireflective dielectric layers and the antireflective dielectriclayers may have different AV/Zn ratios from each other.

Each overlying barrier protects its underlying silver layer fromoxidation during sputter deposition of its overlying ZnAlOx oxide layer.Whilst further oxidation of these barriers layers may occur duringdeposition of their overlying oxide layers a portion of these barrierspreferably remains in the form of an oxide that is not fully oxidised toprovide a barrier for subsequent heat treatment of the glazing panel.

The glazing sheet carrying the sputtered double silver coating stack issubsequently heated, bent to its desired curvature and assembled with asheet of pvb into a laminated vehicle windscreen which has the followingproperties:

Prior to heat Following heat treatment^(see Note 1) treatment^(see Note 2) Property ^(below) ^(below) TL (Illuminant A) 63% 76% TE(System Moon 2) 38% 42% haze 0.1 0.25 a* −20 (coated side)  −6(external) b*  +3 (coated side) −12 (external) RE (System Moon 2) 31%(coated 33% (external) side) ^(Note 1)Measured for monolithic glazingpanel with coating prior to heat treatment ^(Note 2)Measured followingheat treatment at 650° C. for 10 minutes followed by bending andtempering, and lamination with clear 2 mm glass sheet and 0.76 mm clearpvb

Heat treatment preferably causes substantially complete oxidation of allof the barrier layers such that the structure of the coating stack afterheat treatment is:

Geometrical thickness Atomic ratios Glass substrate 2 mm Base dielectriccomprising: AlN (partially oxidized)  60 Å ZnAlOx 250 Å Al/Zn = 0.1ZnAlOx (oxidised underlying  10 Å-16 Å Al/Zn = 0.1 barrier) Ag 100 ÅZnAlOx (oxidised overlying  12 Å-20 Å Al/Zn = 0.1 barrier) Centraldielectric comprising ZnAlOx 750 Å Al/Zn = 0.1 ZnAlOx (oxidisedunderlying  7 Å-12 Å Al/Zn = 0.1 barrier) Ag 100 Å ZnAlOx (oxidisedoverlying  17 Å-28 Å barrier) Top dielectric comprising: ZnAlOx 185 ÅAl/Zn = 0.1 AlN (partially oxidised)  85 Å

The AIN (partially oxidised) layers may comprise a mixture of AIN andAl₂O₃, the AIN being partially oxidised during the heat treatmentprocess. The barrier layers are not necessarily completely oxidised andtheir thickness will depend to a certain extent upon their degree ofoxidation.

The coating layer 25 is spaced from the external periphery of thewindscreen by a non-conducting peripheral band (not shown) provided inthis is example by a band in which the coating layer has either not beendeposited or has been removed. This prevents the electrically conductivecoating extending to the very edge of the windscreen and may also reducethe risk of corrosion of the coating layer.

Electrical power is supplied to the coating layer via a first bus bar 31arranged in contact with the coating layer 25 adjacent to the top edge21 of the windscreen and a second bus bar 32 arranged in contact withthe coating layer 25 adjacent to the bottom edge 23 of the windscreen.Connectors 33,34 for facilitating connection of the bus bars to a car'selectrical circuit may protrude from the glazing and may be arrangedadjacent to each other. The first bus bar has a portion which runs downthe side edge 22 of the windscreen along a portion of the glazing panel11 to at which the coating layer 25 is not present so that there is noelectrical connection between this portion of the bus bar and thecoating layer. This allows the connector 33 to be positioned at thebottom edge 22 of the windscreen. The bus bars may be formed in anysuitable manner, for example by silk screen printing of a conductingenamel material underneath or on top of the coating layer or by means ofconducting tape or metal strips.

FIGS. 2,3 and 4 illustrate the curvature and dimensions of the glazing,the significant measurements in this case being:

-   -   w the width of the glazing window    -   r the radius of curvature of the glazing panel. Different        portions of the glazing panel will have different radii of        curvature    -   cc the cross curvature of the windscreen. The cross curvature        may be measured by placing the convex surface 13 of the        windscreen on a surface, placing a straight, rigid bar at the        concave face of the windscreen along axis y such that the bar        rests against a point at the top edge 21 of the windscreen and        against a point at the bottom edge 23 of the windscreen and        measuring the distance between the underside of the bar and the        concave surface of the windscreen. The maximum cross curvature        is the maximum distance, usually at the centre of the        windscreen, which the windscreen has been bent parallel to axis        y.    -   d the depth of the windscreen. The maximum depth is the maximum        distance measured parallel to axis z between the outer surface        of the convex surface of the laminated windscreen 13 and the        furthest spaced portion on the side wings of the windscreen.

1. A method of manufacturing a curved laminated automotive glazingpanel, comprising the steps of: (a) depositing a solar control coatinglayer comprising a coating stack having at least two spaced sputteredsilver containing layers on a substantially flat sheet of glazingmaterial; (b) bending said substantially flat sheet of glazing materialcarrying said solar control coating layer such that the solar controlcoating layer is positioned at a convex surface of the bent sheet ofglazing material; (c) laminating said bent sheet of glazing materialcarrying the solar control coating layer at a convex surface withanother sheet of glazing material to form a glazing panel in which thesolar control coating layer is positioned at the interior of the glazingpanel; and wherein the laminated automotive glazing panel is curvedaccording to at least one of the following (d) and (e): (d) the curvedlaminated automotive glazing panel has at least one portion having aradius of curvature that is less than 500 mm; (e) the curved laminatedautomotive glazing panel has a cross curvature of greater than or equalto 15 mm.
 2. A method of manufacturing a curved laminated automotiveglazing panel, comprising the steps of: (a) depositing a solar controlcoating layer comprising a coating stack having at least two spacedsputtered silver containing layers on a substantially flat sheet ofglazing material; (b) bending said substantially flat sheet of glazingmaterial carrying said solar control coating layer such that the solarcontrol coating layer is positioned at a convex surface of the bentsheet of glazing material; (c) laminating said bent sheet of glazingmaterial carving the solar control coating layer at a convex surfacewith another sheet of gazing material to form a glazing panel in whichthe solar control coating layer is positioned at the interior of theglazing panel; and wherein the laminated automotive glazing panel iscurved according to both of the following (d) and (e); (d) the curvedlaminated automotive glazing panel has at least one portion having aradius of curvature that is less than 500 mm; (e) the curved laminatedautomotive glazing panel has a cross curvature of greater than or equalto 15 mm.
 3. A method according to claim 1, and further including atleast one of the following (f) through (m): (f) the curved laminatedautomotive glazing panel has a depth of bending that is greater than orequal to 150 mm; (g) the coating layer is adapted to be electricallyheatable to provide a de-icing and/or de-icing function to the glazingpanel and in which the glazing panel is provided with a pair of spacedbus bars adapted to relay electrical power to heat the solar controlcontaining layer; (h) the curved laminated automotive glazing panel hasa width of greater than about 1.6 m; (i) the curved laminated automotiveglazing panel has a luminous transmittance of at least 75% (measuredusing Illuminant A, 2 degree observer); (j) the colour co-ordinates ofthe curved laminated automotive glazing panel in reflection from theexterior measured on the CIElab scale at normal incidence are within therange: $\begin{matrix}{L^{*} = {40 \pm 3}} & {a^{*} = {{- 6} \pm 3}} & {{b^{*} = {{- 8} \pm 4}};{or}} \\{L^{*} = {39 \pm 3}} & {a^{*} = {{- 6} \pm 3}} & {{b^{*} = {{- 2} \pm 4}};{or}} \\{L^{*} = {36 \pm 3}} & {a^{*} = {{- 5} \pm 2}} & {{b^{*} = {{- 4} \pm 2}};}\end{matrix}$ (k) colour variation in reflection over the surface of theglazing panel is such that when measured at different points over asingle glazing, the values of a* and/or b* measured on the CIElab scaleat normal incidence do not vary but more than ±1.5; (l) the electricalresistance of the coating layer is between 1.5 and 4 ohms per square;and (m) the glazing panel is provided with a pair of spaced bus barsadapted to provide electrical power to heat the solar control coatinglayer and in which the resistance between the bus bars is between about0.75 and 8 ohms.
 4. A method according to claim 3, and including atleast two of the aforementioned features (f) through (m).
 5. A method ofmanufacturing a curved laminated automotive glazing panel, comprisingthe steps of: (a) depositing a solar control coating layer comprising acoating stack having at least two spaced sputtered silver containinglayers on a substantially flat sheet of glazing material; (b) bendingsaid substantially flat sheet of glazing material carrying said solarcontrol coating layer such that the solar control coating layer ispositioned at a convex surface of the bent sheet of glazing material;(c) laminating said bent sheet of glazing material carrying the solarcontrol coating layer at a convex surface with another sheet of glazingmaterial to form a glazing, panel in which the solar control coatinglayer is positioned at the interior of the glazing panel; and whereinthe laminated automotive glazing panel is curved according to at leastone of the following (d) and (e): (d) the curved laminated automotiveglazing panel has at least one portion having a radius of curvature thatis less than 500 mm; (e) the curved laminated automotive glazing, panelhas a cross curvature of greater than or equal to 15 mm; the methodincluding at least three of the following features (f) through (m); (f)the curved laminated automotive glazing panel has a depth of bendingthat is greater than or equal to 150 mm; (g) the coating layer isadapted to be electrically heatable to provide a de-misting and/orde-icing function to the glazing panel and in which the glazing panel isprovided with a pair of spaced bus bars adapted to relay electricalpower to heat the solar control containing layer; (h) the curvedlaminated automotive lazing panel has a width of greater than about 1.6m; (i) the curved laminated automotive glazing panel has a luminoustransmittance of at least 75% (measured using Illuminant A, 2 degreeobservers); (j) the colour co-ordinates of the curved laminatedautomotive glazing panel in reflection from the exterior measured on theCIElab scale at normal incidence are within the range: L* = 40 ± 3 a* =−6 ± 3 b* = −8 ± 4: or L* = 39 ± 3 a* = −6 ± 3 b* = −2 ± 4; or L* = 36 ±3 a* = −5 ± 2 b* = −4 ± 2;

(k) colour variation in reflection over the surface of the glazing panelis such that when measured at different points over a single glazing,the values of a* and/or b* measured on the CIElab scale at normalincidence do not vary but more than ±1.5; (l) the electrical resistanceof the coating layer is between 1.5 and 4 ohms per square; and (m) theglazing panel is provided with a pair of spaced bus bars adapted toprovide electrical power to heat the solar control coating layer and inwhich the resistance between the bus bars is between about 0.75 and 8ohms.
 6. A method according to claim 5, and including all of theaforementioned features (f) through (m).
 7. A method according to claim1, and including at least one of the following (n) through (p): (n) theglazing panel has a radius of curvature at said at least one portionthat is less than 400 mm; (o) the glazing panel has a radius ofcurvature at said at least one portion that is less than 350 mm; (p) theglazing panel has a radius of curvature at said at least one portionthat is less than 300 mm.
 8. A method of manufacturing a curvedlaminated automotive glazing panel, comprising the steps of: (a)depositing a solar control coating layer comprising a coating stackhaving at least two spaced sputtered silver containing layers on asubstantially flat sheet of glazing material; (b) bending saidsubstantially flat sheet of glazing material carrying said solar controlcoating layer such that the solar control coating layer is positioned ata convex surface of the bent sheet of glazing material; (c) laminatingsaid bent sheet of glazing material carrying the solar control coatinglayer at a convex surface with another sheet of lazing material to forma glazing panel in which the solar control coating layer is positionedat the interior of the glazing panel; and wherein the laminatedautomotive glazing panel is curved according to at least one of thefollowing (d) and (e); (d) the curved laminated automotive glazing panelhas at least one portion having a radius of curvature that is less than500 mm; (e) the curved laminated automotive glazing panel has acrosscurvature of greater than or equal to 15 mm; wherein the glazing panelhas at least one of the following features (q) through (s); (q) theglazing panel has a cross curvature of greater than or equal to 20 mm;(r) the glazing panel has a cross curvature of greater than or equal to25 mm; (s) the glazing panel has a cross curvature of greater than orequal to 30 mm.
 9. A method according to claim 3, including theaforementioned (g) and wherein the glazing panel is provided with asubstantially opaque band arranged at the internal, concave surface ofthe glazing panel adapted to mask the bus bars from view from theexterior of the glazing panel.
 10. A method according to claim 1, inwhich the glazing panel is an automotive windscreen.
 11. A curvedlaminated automotive glazing panel, comprising: (a) a solar controlcoating layer comprising a coating stack, said solar control coatinglayer positioned at the convex internal surface of the glazing panel;(b) said coating stack having at least two spaced sputtered silvercontaining layers, wherein the solar control coating layer is sputterdeposited on a surface of a first substantially flat sheet of glazingmaterial which is subsequently bent such that the solar control coatinglayer is at a convex surface of said first sheet of glazing material;(c) another sheet of glazing material laminated to said first sheet ofglazing material having said solar control coating layer positionedthereon, to form a glazing panel in which the solar control coatinglayer is positioned at the interior of the glazing panel; and whereinthe laminated automotive glazing panel is curved according to at leastone of the following (d) and (e); (d) the curved laminated automotiveglazing panel has at least one portion having a radius of curvature thatis less than 500 mm; (e) the curved laminated automotive glazing panelhas a cross curvature of greater than or equal to 15 mm.
 12. A curvedlaminated automotive glazing panel, comprising: (a) a solar controlcoating layer comprising a coating stack, said solar control coatinglayer positioned at the convex internal surface of the glazing panel;(b) said coating stack having at least two spaced sputtered silvercontaining layers on a first substantially flat sheet of glazingmaterial which is subsequently bent such that the solar control coatinglayer is at a convex surface of said first sheet of glazing material;(c) another sheet of glazing material laminated to said first sheet ofglazing material having said solar control coating layer positionedthereon, to form a glazing panel in which the solar control coatinglayer is positioned at the interior of the glazing panel; and whereinthe glazing panel is curved according to both of the following (d) and(e); (d) the curved laminated automotive glazing panel has at least oneportion having a radius of curvature that is less than 500 mm; (e) thecurved laminated automotive glazing panel has a cross curvature ofgreater than or equal to 15 mm.
 13. A glazing panel according to claim11, and further including at least one of the following (f) through (m):(f) the curved laminated automotive glazing panel has a depth of bendingthat is greater than or equal to 150 mm; (g) the coating layer isadapted to be electrically heatable to provide a de-misting and/orde-icing function to the glazing panel and in which the glazing panel isprovided with a pair of spaced bus bars adapted to relay electricalpower to heat the solar control containing layer; (h) the curvedlaminated automotive glazing panel has a width of greater than about 1.6m; (i) the curved laminated automotive glazing panel has a luminoustransmittance of at least 75% (measured using Illuminant A, 2 degreeobserver); (j) the colour co-ordinates of the curved laminatedautomotive glazing panel in reflection from the exterior measured on theCEIlab scale at normal incidence are within the range: L* = 40 ± 3 a* =−6 ± 3 b* = −8 ± 4: or L* = 39 ± 3 a* = −6 ± 3 b* = −2 ± 4; or L* = 36 ±3 a* = −5 ± 2 b* = −4 ± 2;

(k) colour variation in reflection over the surface of the glazing panelis such that when measured at different points over a single glazing,the values of a* and/or b* measured on the CEIlab scale at normalincidence do not vary but more than ±1.5; (l) the electrical resistanceof the coating layer is between 1.5 and 4 ohms per square; and (m) theglazing panel is provided with a pair of spaced bus bars adapted toprovide electrical power to heat the solar control coating layer and inwhich the resistance between the bus bars is between about 0.75 and 8ohms.
 14. A glazing panel according to claim 13, and including at leasttwo of the aforementioned features (f) through (m).
 15. A curvedlaminated automotive glazing panel, comprising: (a) a solar controlcoating layer comprising a coating stack, said solar control coatinglayer positioned at the convex internal surface of the glazing panel;(b) said coating stack having at least two spaced sputtered silvercontaining layers on a first substantially flat sheet of glazingmaterial which is subsequently bent such that the solar control coatinglayer is at a convex surface of said first sheet of glazing material;(c) another sheet of glazing material laminated to said first sheet ofglazing material having said solar control coating layer positionedthereon, to form a glazing panel in which the solar control coatinglayer is positioned at the interior of the glazing panel; and whereinthe laminated automotive glazing panel is curved according to at leastone of the following (d) and (e); (d) the curved laminated automotiveBlazing panel has at least one portion having a radius of curvature thatis less than 500 mm; (e) the curved laminated automotive glazing panelhas a cross curvature of greater than or equal to 15 mm; the glazingpanel further including at least three of the following features (f)through (m); (f) the curved laminated automotive glazing panel has adepth of bending that is greater than or equal to 150 mm; (g) thecoating layer is adapted to be electrically heatable to provide ade-misting and/or de-icing function to the glazing panel and in whichthe gazing panel is provided with a pair of spaced bus bars adapted torelay electrical power to heat the solar control containing layer; (h)the curved laminated automotive glazing panel has a width of greaterthan about 1.6 m; (i) the curved laminated automotive glazing panel hasa luminous transmittance of at least 75% (measured using Illuminant A, 2degree observer); (j) the colour co-ordinates of the curved laminatedautomotive glazing panel in reflection from the exterior measured on theCIElab scale at normal incidence are within the range: L* = 40 ″ 3 a* =−6 ″ 3 b* = −8 ″ 4; or L* = 39 ″ 3 a* = −6 ″ 3 b* = −2 ″ 4; or L* = 36 ″3 a* = −5 ″ 2 b* = −4 ″ 2;

(k) colour variation in reflection over the surface of the glazing panelis such that when measured at different points over a single glazing,the values of a* and/or b* measured on the CIElab scale at normalincidence do not vary but more than “1.5; (l) the electrical resistanceof the coating layer is between 1.5 and 4 ohms per square; and (m) theglazing panel is provided with a pair of spaced bus bars adapted toprovide electrical power to heat the solar control coating layer and inwhich the resistance between the bus bars is between about 0.75 and 8ohms.
 16. A glazing panel according to claim 15, and including all ofthe aforementioned features (f) through (m).
 17. A glazing panelaccording to claim 12, and including at least one of the following (n)through (p); (n) the glazing panel has a radius of curvature at said atleast one portion that is less than 400 mm; (o) the glazing panel has aradius of curvature at said at least one portion that is less than 350mm; (p) the glazing panel has a radius of curvature at said at least oneportion that is less than 300 mm.
 18. A glazing panel according to claim12, and including at least one of the following (q) through (s): (q) theglazing panel has a cross curvature of greater than or equal to 20 mm;(r) the glazing panel has a cross curvature of greater than or equal to25 mm; (s) the glazing panel has a cross curvature of greater than orequal to 30 mm.
 19. A glazing panel according to claim 13, including theaforementioned (g) and wherein the glazing panel is provided, with asubstantially opaque band arranged at the internal, concave surface ofthe glazing panel adapted to mask the bus bars from view from theexterior of the glazing panel.
 20. A glazing panel according to claim11, in which the glazing panel is an automotive windscreen.
 21. Themethod of claim 1, wherein the glazing material is glass.
 22. The methodof claim 2, wherein the glazing material is glass.
 23. The method ofclaim 5, wherein the glazing material is glass.
 24. The method of claim8, wherein the glazing material is glass.
 25. The glazing panel of claim11, wherein the glazing material is glass.
 26. The glazing panel ofclaim 12, wherein the glazing material is glass.
 27. The glazing panelof claim 15, wherein the glazing material is glass.